The long-term objective of this project is twofold. First, our aim is to study cell-to-cell communication in the vertebrate taste buds. We will investigate taste buds in amphibia (Necturus maculosus) and in mammals (hamsters, rabbits, mice). One of our Specific Aims is to investigate which neurotransmitters are involved at synapses in taste organs. We plan to use a battery of neurochemical and molecular biological techniques, including immunocytochemistry, quantitative autoradiography, and high pressure liquid chromatography with electrochemical detection. We will determine which transmitters are present in taste buds; which ones are taken up by taste cells and released by calcium-dependent mechanisms when the cells are stimulated; and where the transmitters are localized. We will also study electrical synapses between taste cells and the localization of gap junction proteins. Second, we will study the function of Merkel-like basal cells and their putative role in neuromodulation of taste bud function. Merkel-like basal cells contain high concentrations of serotonin, among other substances and release the monoamine when they are depolarized. We will investigate whether serotonin is a neuromodulator of taste bud function in amphibia and in mammals. In the broad view, our experiments may lead to the rational design of pharmaceutical agents that can suppress, enhance or modify taste since we will determine what neurotransmitters are acting in the taste organs and since our data will lead to an understanding of how chemicals act on the apical, chemosensory membrane of taste cells.